Find functions with pragma RESTRICT_REFERENCES

If you want to do parallel DML and use packaged functions in the statement, the functions need to fulfill certain requirements. Otherwise you will get the following note in the plan and PDML is not used:
- PDML disabled because function is not pure and not declared parallel enabled

The parallel enabled requirement is easy to check, you can find it out by querying DBA_PROCEDURES.PARALLEL

Pure functions

The second one is a bit harder, because it is not directly exposed via a database view.
First we need to know what pure means in this case. A function is considered as pure if it is defined with the pragma RESTRICT_REFERENCES and all four constraints RNDS, WNDS, RNPS and WNPS.

This information is encoded in SYS.PROCEDUREINFO$.PROPERTIES. The following query can be used to display which constraints of the pragma are used in a function/procedure:

Conclusion

The above query provides an easy and fast way to determine if a function can be used in PDML statements. This is especially useful if you have a function for which you don’t own the source.

Example: We had a DML statement which was using UTL_I18N.STRING_TO_RAW. This function is neither parallel enabled nor does it have the required pragma RESTRICT_REFERENCES. Therefore no PDML was performed.
We simply changed the statement to use UTL_RAW.CAST_TO_RAW instead, which has the pragma RESTRICT_REFERENCE required for PDML.
Of course these two functions do not provide the exact same functionality, but in our case (destination charset was the same as database charset) we were able to swap them without risk.